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Pelanomodon
Pelanomodon is an extinct genus of dicynodont therapsid. Fossil evidence of this genus is principally found in the Karoo Basin of South Africa, in the Dicynodon Assemblage Zone.1 Lack of fossil record after the Late Permian era suggests that Pelanomodon fell victim to the Permian-Triassic extinction event. The name Pelanomodon can be broken up into three parts; “pelos” meaning mud, “anomo” meaning irregular and “odon” meaning tooth. Together, this suggests Pelanomodon to be a mud dwelling anomodont (a group of theraspids that are characterized by their lack of teeth).2 The Karoo Basin during this period was characterized by its extensive flood plains,3 so to hypothesize a mud based habitat for this genus is not far fetched. Pelanomodon is in the Geikiidae family along with Aulacephalodon and Geikia. Aulacephalodon is believed to have lived along side Pelanomodon in the Karoo Basin, where as records of Geikia have been discovered in Scotland and Tanzania. Pelanomodon is primarily characterized and distinguished from Aulacephalodon by its lack of tusks.1 Other crananial features have been used by paleontologists to establish two species of Pelanomodon; P. moschops and P. rubidgei. However, recent analysis points to the conclusion that these may in fact the same species. Geological and Paleoenvironment The fossil record of Pelanomodon has thus far been restricted to the Karoo Basin in Southern Africa.1 This region chronicles constant sediment accumulation from the Carboniferous period and into the Jurassic period. Pelanomodon, along with other dicynodonts are predominantly found as a part of the Beaufort Group. The Beaufort Group geological strata ranges from the middle Permian to middle Triassic period. Sedimentary analysis suggests that during this time the region was characterized by the extensive flood plains of a few large rivers.3 The climate during the late Permian period, in this region was semi-arid and rainfall was seasonal.4 This climate, combined with the important role that rivers played in establishing the environment, allowed for a variety of riparian vegetation to grow, which in turn lead to a high diversity of animals that were all able to fill a different niche.4 In fact, dicynodonts have been found to be the most abundant therapsid in this range. Discovery and Historical Information Pelanomodon was first discovered by Robert Broom, in the Karoo Basin of South Africa, in 1913. Its classification was based on a nearly complete skull, missing only the lower jaw.6 The species was originally named Dicynodon moschops, however, in 1969 an analysis done by A. W. Keyser reclassified the specimen as Pelanomodon moschops.7 Another species, Pelanomodon rubidgei, was classified by Broom in 1938, and was established from a complete skull found in the same region, by S. H Rubidge.8 Between the years of 1913 and 1950, Broom described five different Pelanomodon species, based on differences observed between many partial, and complete skulls.68910 However, since this time, several paleontologists have re-evaluated the morphology of the skulls and reclassified them all as either Pelanomodon rubidgei or Pelanomodon moschops.711 Since fossil records can never provide a complete understanding of the past, these classifications are still debated among paleontologists. In 2016, a new analysis suggested that the morphological features used to distinguish between Pelanomodon moschops and Pelanomodon rubidgei are actually a result of sexual dimorphism within the same species.1 The same analysis claims that Propelanomodon, another tuskless dicynodont genus, first described by Broom in 1913,6 is in fact a juvenile form of Pelanomodon. The authors of this analysis would classify all these species as Pelanomodon moschops. The basis for these conclusions are discussed below. Description and Paleobiology Category:Dicynodonts Category:Prehistoric synapsids of Africa Category:Anomodonts